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The treatment protocols for many neoplasms include radiotherapy. It is almost always performed after the surgical removal of the cancer, with the aim of destroying any tumor cells that may have remained in the area where the primary tumor was located or where the metastases were.

This cancer treatment is called adjuvant, while neoadjuvant is the one that aims to reduce the size of the primary tumor before surgery. Radiotherapy can also be used to reduce the size of the tumor for palliative purposes, for example in the case of bone metastases, or as the main treatment of specific tumors, such as those of the head and neck or that of the rectum.

Selectivity of Radiotherapy on Cancer Cells

The purpose of administering radiation to a tumor is to damage the DNA of its constituent cells. On the other hand, if it is true that radiotherapy damages both normal cells and that both are able to repair the damage suffered, it is equally true that the degree of damage they receive from radiation depends on the intensity of the replication processes that affect them. Cancer cells are more damaged, because their replication index is higher, and they take longer to repair the damage they have suffered.

Radiation Therapy Regimens – Dose Splitting

Radiotherapy is generally not administered on a single occasion, but is divided into a series of small daily doses, scheduled at well-defined intervals, over a period of 3-7 weeks. These protocols are called dose fractionation and are calculated in such a way as to allow the repair of damage to healthy cells affected by radiation, but not to those of cancer. This method of administration also reduces the risk of long-term side effects from radiotherapy.

Radiation doses are measured in units called Gray (abbreviated to Gy). For tumors composed of cells with a particularly high rate of replication, using a type of radiotherapy called continuous hyperfractionated accelerated radiotherapy, which has provided benefits in the treatment of lung and head and neck cancers.

Method of Administration of Radiotherapy

Usually the treatments are performed with the patient lying down on a special support and a concentrated beam of ionizing radiation, calculated very accurately, is directed on the tumor. This technique is called external collimated beam radiation therapy. The radiation is directed in such a way as to hit as little healthy tissue as possible. In recent years, the accuracy and safety of radiotherapy procedures has greatly improved with an approach called conformational radiotherapy. It is based on the use of computerized systems which, starting from the results of imaging tests such as CT and magnetic resonance, create a three-dimensional graphic representation of the tumor.

On this “model” of the neoplasia the systems themselves calculate the direction and shape of the beam, the intensity of the radiation dose and the duration of exposure. The computer it also controls the administration of radiation. Whatever radiotherapy procedure is used, the actual administration of rays only takes a few minutes, but the preparation of the patient can take some time.

In fact, on the one hand it is necessary to ensure that he does not move during the administration of the radiation, to be sure that they keep the “target” on the cancer, and on the other hand, it is necessary to protect the parts of the body that are not to be irradiated and which could be damaged by the spokes. In addition, some protocols provide for the preventive administration of drugs that increase the sensitivity of the tumor to radiotherapy or substances that reduce the risk of damage to healthy tissues.

A particular type of radiotherapy treatment is the one called brachytherapy. It provides that a radioactive substance, such as iridium 192, is placed in direct contact with carcinomas, by implanting small containers locally. The technique is mainly used for cancer of theprostate, of the ‘neck cancer utero and for some cancers of the head and neck, such as that of language.

This treatment is based on the principle that radiation exposure decreases rapidly as the distance from the radioactive material increases and, therefore, it is better to concentrate the radioactivity on the small area where the implant is located and, the person treated with this approach, does not emit radiation that can reach others, so he can usually return home, after applying the device.

The radioactivity gradually fades and the implant does not need to be removed. However, sometimes a very high dose is given with brachytherapy, which can be left in place for up to two days. During this period of time the patient must remain hospitalized and limit contact with other people.